Basic Electrical Safety Faculty of Science & Health - PowerPoint PPT Presentation

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Basic Electrical Safety Faculty of Science & Health

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  1. BasicElectrical SafetyFaculty of Science & Health Safe Lab Module January 2008 January 2008 Ver 1.1

  2. Electrical SafetyatDCU Electrical Safety Awareness Electricity basics & few simple pointers Specific laboratory examples, A few Do’s & Don’ts & Watch out for’s January 2008 Ver 1.1

  3. Content • [ I ] Basic Electrical Theory[ Ladybird version, no maths ! ] • Voltage & current • Electricity in the body & effects on the body • Electricity & associated hazards • [ II ] Electrical Appliances • Safety features, cables, connections, design • General Electrical Guidelines & Precautions • Electrocution • [ III ] Specific Hazards & Personal Safety January 2008 Ver 1.1

  4. [ I ]Electricity January 2008 Ver 1.1

  5. Basic Electrical Theory • Voltage [driving force] causes current [e - ] to flow • AC / DC - from safety perspective - negligible difference • Single Phase / Three Phase. 3 get a professional • Circuit / loop is necessary for current to flow • a start point - a route - an end point January 2008 Ver 1.1

  6. Voltage, Current and Resistance • Voltage increases => Current increases • Resistance decreases => Current increases Voltage = Current / Resistance - Ohms Law January 2008 Ver 1.1

  7. The complete circuit A complete Circuit or loop is necessary for current to flow January 2008 Ver 1.1

  8. A complete circuit complete Circuit or loop is necessary for current to flow Current takes the path of least resistance January 2008 Ver 1.1

  9. Basic Electrical Theory • Voltage causes a Current to flow • Water analogy • A complete Circuit is necessary for current to flow • Bird on HT wires January 2008 Ver 1.1

  10. Voltages • Low Tension 0 => 50V • Batteries: AA, AAA, MP3 player • Car, trucks, busses 12 / 24 / 48 • Garden lights, domestic halogen lights • High Tension 100 => 300V • EU Mains, Electrophoresis, DART, Capacitors SM PSUs • Very High Tension 1KV + • ESB pylons, TV tubes, photocopiers, X-Ray machines, Mass Spectrometers January 2008 Ver 1.1

  11. Electricity in the body January 2008 Ver 1.1

  12. Electricity in the body • Muscles • Muscles control all the body movements • Including & importantly those that keep us alive - Breathing and Heart • The brain controls voluntary muscles using Current pulses along nerves January 2008 Ver 1.1

  13. Electricity in the body • External currentthrough the body causes • Loss of muscle control • Spasms & Involuntary movement • Inability to let go • Burns - external & internal January 2008 Ver 1.1

  14. Electricity&associated hazards January 2008 Ver 1.1

  15. Electricity - associated Hazards • Indirect Injury • Falls from ladder • Thrown back. Fall to ground, onto sharp edge • Drop objects • Thermal burns – Very hot equipment surface, explosion • Wires & cables - Trailing leads => trips & damage, Re-route, tidy up, cover over • Life Support muscles • Diaphragm and breathing • Heart Fibrillation Random, uncoordinated heart contractions • De-fribrillation: High voltages (3000 V at 20 A) fraction of a second • Burns - death of tissue • Internal [organs] • External [skin] January 2008 Ver 1.1

  16. END[ I ] Electrical Theory Section January 2008 Ver 1.1

  17. Electrical Appliances Safety guiding principle “keep currents and voltages inside apparatus and away from our bodies” • Inherently safe - Low voltage / low current • Enclosures • Insulation • Safe & secure connections January 2008 Ver 1.1

  18. Electrical cables & plugs Mains cable • Brown Live - power • Blue Neutral • Green/yellow Earth January 2008 Ver 1.1

  19. Electrical cables & plugs Mains cable • Brown Live power • Blue Neutral • Green/yellow Earth L N January 2008 Ver 1.1

  20. L N L N E Live, Neutral, Earth & Fuses January 2008 Ver 1.1

  21. Live, Neutral, Earth & Fuses L N January 2008 Ver 1.1

  22. RCD Residual Current Device RCCB Residual Current Circuit Breaker ELCB Electric Leakage Circuit Breaker MCB Magnetic Circuit Breakers RCBO Residual Current Breaker with Overcurrent protection • current difference of >30 mA • for a duration of >30 ms L L N N E January 2008 Ver 1.1

  23. Live, Neutral, Earth & Fuses • The Live and Neutral wires carry current around the circuit • The Earth wire is there to protect you. • The Earth wire can act like a back-up Neutral wire, • Many appliances have metal cases e.g. kettles, toasters, dishwashers, washing machines etc. • The Fuse is very thin piece of wire. • The wire has a quite low melting point. As current flows through the wire it heats up. • If too large a current flows it melts, thus breaking the circuit • Use appropriate fuse size/rating • Additional safety devices - RCDs, ELCBs, MCBs January 2008 Ver 1.1

  24. Guidelines • Use low & safe voltages • EU 230 VAC / US 110 VAC Hz • Select equipment appropriate for environment & use • Use equipment as per manufacturer’s instruction & design • Ensure adequate maintenance • Insulate and enclose live parts • Prevent conducting parts from becoming live. Earth, double insulation separate supply from earth, limit electric power • Avoid electricity where its use could be dangerous. Rubbing, Induction & Capacitance effects can build up static electricity • Toxic - Berilium heat sinking, Incomplete burning can produce carbon monoxide January 2008 Ver 1.1

  25. END[ II ] Electrical Appliances January 2008 Ver 1.1

  26. Electrocution • Prevention & Training : Where are red mushroom switches ? • Response: Immediately cut power, red buttons / switch / plug • If in any doubt - Do not touch victim. • One hand behind back, stand on insulation, tip with back of hand • Use insulating rod / stick to move wires from victim. • Call for assistance • Talk & reassure victim • If unconscious then use first aid, CPR January 2008 Ver 1.1

  27. Electrical Hazards & Personal Safety • Where • Office & home 95% • Laboratory 5% • Trailing wires, faulty wires • Mains • Avoid direct working with mains. Use only low voltages (tension ) • Check all leads for: Fraying, Proper clamping, Proper earthing. • Repairing • Do not repair, competency required • One hand behind back, tip cautiously with back of hand • Trust nobody, remove fuse, use phase tester Note: Switch Mode PSU, laptop chargers, CF lamps [high voltages persists on capacitors long after switch off] January 2008 Ver 1.1

  28. Specific Hazards & Personal Safety • Medical / sports equipment • Very strict regulations on equipment operation, design, repair • Never modify or tamper with such equipment • ECG measurements. even a few micro amps in a susceptible location can have massive consequences [Basis of Heart pacemaker ] • Pace makers • Susceptible to strong magnetic fields [NMR! ], • Possibly RF & Micro waves • Solvent • Flammable environments require specialised electrical equipment E.g. Fridge storage of samples stored in solvents • Cold rooms / water cooling • Equipment moved from a cold room with get condensation on its internal electrical • circuits Avoid this movement, Use LT, give lots of time to acclimatise January 2008 Ver 1.1

  29. Specific Hazards & Personal Safety • RF & µW • Capacitive coupling, no need to touch, • Both can burn severely internally and externally depending on how focused. Think of them like an open air μ-wave oven • HT • Static, OK [Very low current, moderate power] • Will jump considerable distances, beware of capacitors • Power • Heating effect in body => internal burns / damage • Contact burns, deep burns & necrosis • Trailing power and signal wires - Protect & Tidy them up January 2008 Ver 1.1

  30. Specific Hazards & Personal Safety • Other Laboratory Situations • Other Office Situations • Other Home Situations January 2008 Ver 1.1

  31. Where to get more Information • Your Supervisor, Manager, Head of Department • Department Safety Statements • Department Safety Committees & Safety Officer • DCU safety - WEB • Edinburgh H&S - WEB • University London H&S - WEB January 2008 Ver 1.1

  32. Summary • Awareness of the need for electrical safety • Introduction to the source of electrical dangers • Your responsibility to take care of yourself and others January 2008 Ver 1.1

  33. END January 2008 Ver 1.1

  34. What’s the problem? January 2008 Ver 1.1